1. Field of the Invention
The present invention is directed to an improvement in rotary volumetric motors.
2. Description of the Prior Art
There are two main categories of motors among heat engines which transform the thermal energy provided by fuel into mechanical energy. First, continuous flow motors of the gas turbine type can be used which operate according to the Joule cycle. Secondly, volumetric motors can be used wherein compression and expansion are obtained by volume variation and which operate according to the Beau de Rochas (gasoline engines) or Diesel cycle.
None of the motors which fall into these two categories is completely satisfactory insofar as the continuous flow motors have an advantage over the others in that they are lighter, which makes them preferable for use as aircraft engines, but their specific fuel consumption is high, on the order of 200 g per horsepower hour for large gas turbines, a figure which can increase to 300 or more for small gas turbines. Moreover, gas and Diesel volumetric motors are heavy and cumbersome, which is a serious disadvantage but is in general acceptable for terrestrial motors because of their low specific fuel consumption (Diesel motors may have specific fuel consumption levels on the order of 150 g per horsepower hour).
The differences in specific fuel consumption between continuous flow and volumetric motors expressed above are based on optimum operating conditions at a constant load for both types of machines. These differences are even greater when the motors are operating under a partial load, wherein the specific fuel consumption of continuous flow engines increase rapidly when the load is reduced while, on the contrary, the specific fuel consumption of Diesel engines varies only slightly and may even improve when the load is reduced.
Applicant's analysis of this matter has resulted in the following comments and led to the development of the present invention. One of the main reasons for the low fuel consumption of volumetric motors lies in the fact that compression and expansion occur volumetrically, so that compression and expansion yields are very near 1. As a first approximation, it is generally considered that compression and expansion are isotropic. On the other hand, compression and expansion in a continuous flow motor occur with a yield substantially lower than 1. Despite the progress achieved since the development of turbomachines, the compression yield is on the order of 88% and the expansion yield is on the order of 90%. In addition, these figures apply only to turbomachines of large size (and within a narrow operating range), while small turbomachines (or large ones operating outside this range) have yields that are even further from the yield of unity which has almost been achieved by Diesel motors.
One of the main objectives of this invention is to have compression and expansion occur volumetrically, so as to take advantage of the near-unity yields provided by this kind of compression or expansion. On the other hand, the low fuel consumption of volumetric motors is also due to the fact that the efficient temperature to be taken into consideration in the cycle is very near the practically continuously), the maximum temperature of the combustion chamber must be limited, given the actual state of metallurgical knowhow. Even if a stoichiometric temperature is reached locally in the combustion chamber, the most efficient temperature, that is the temperature that conditions the yield of the cycle, is much lower.